Problem with P89V51RD2 interfacing with GSM module (SIM900)

Discussion in 'Embedded Systems and Microcontrollers' started by g_shyam1682, May 29, 2013.

  1. g_shyam1682

    Thread Starter New Member

    Jan 25, 2010
    5
    0
    Hello friend,

    I have one problem with my GSM base project.
    In my project, i use P89v51Rd2 means 5V microcontroller and my GSM module (SIM900) is working at 4.2V, so how can i connect my Micro RX, TX which is at 5V to SIM900 RX, TX which is 4.2V support.

    Please help me to design my circuit.
    Thanks in advance.

    Regards,
    Ghanshyam
     
  2. binu_ji

    Member

    Jul 13, 2007
    22
    1
    SIm900 tx/rx can work with 5v microcontrollers. You can directly connect microcontroller tx/rx to sim rx/tx.

    For sim900 power supply just place a 1n4007 diode which drops 0.7V from 5v.
     
    mkbutan likes this.
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